There are few solutions - more moderators, newbie jail, restrict newbies from posting in altcoin ann/bounty etc. I know even better solution for this problem - trash all threads whose starters don't report spam inside their threads, but choose to reply to them.
Problem is most of these bumping accounts are not directly breaking forum rules as they are asking questions, but if the same question keep repeating over and over again then it is spam(in my opinion).